Magnetic-free non-reciprocal circuits based on sub-harmonic spatio-temporal conductance modulation

ABSTRACT

A circuit comprising a differential transmission line and eight switches provides non-reciprocal signal flow. In some embodiments, the circuit can be driven by four local oscillator signals. The circuit can be used to form a gyrator. The circuit can be used to form a circulator. The circuit can be used to form three-port circulator than can provide direction signal flow between a transmitter and an antenna and from the antenna to a receiver. The three-port circulator can be used to implement a full duplex transceiver that uses a single antenna for transmitting and receiving.

BACKGROUND

Full-duplex communications, in which a transmitter and a receiver of atransceiver operate simultaneously on the same frequency band, isdrawing significant interest for emerging 5G communication networks dueto its potential to double network capacity compared to half-duplexcommunications. Additionally, there are several efforts underway toinclude simultaneous transmit and receive functionality in the nextgeneration phased array radar systems, especially in commercialautomotive radars which can be an enabler technology for futureconnected or driverless cars. However, one of the biggest challengesfrom an implementation perspective is the antenna interface.

One way in which an antenna interface for a full-duplex transceiver canbe implemented is using a non-reciprocal circulator. Reciprocity inelectronics is a fundamental property of linear systems and materialsdescribed by symmetric and time-independent permittivity andpermeability tensors. Non-reciprocity causes signals to travel in onlyone direction. For example, non-reciprocity in a circulator causessignals to travel in only one direction through the circulator. Thisdirectional signal flow enables full-duplex wireless communicationsbecause signals from the transmitter are only directed toward theantenna (and not the receiver) and received signals at the antenna areonly directed toward the receiver (and not the transmitter). Moreover,the receiver is isolated from signals from the transmitter, preventingdesensitization and possible breakdown of the receiver due to thehigh-power transmitted signal.

Conventionally, non-reciprocal circulators have been implemented usingferrite materials, which are materials that lose their reciprocity underthe application of an external magnetic field. However, ferritematerials cannot be integrated into CMOS IC technology. Furthermore, theneed for an external magnet renders ferrite-based circulators bulky andexpensive.

Accordingly, new mechanisms for implementing non-reciprocity in circuitsis desirable.

DETAILED DESCRIPTION

FIGS. 1A, 1B, 1C, and 1D show an example of how a non-reciprocal phaseshift can be implemented in some embodiments.

Turning to FIG. 1A, it can be seen that a signal cos(ω_(in)t) can beinjected at nodes A. This is represented in graph 101 of FIG. 1B. Asshown in FIG. 1A, the switch groups can then be switched by thefollowing signals: cos(ω_(m)t); cos(ω_(m)t+ϕ); sin(ω_(m)t); andsin(ω_(in)t+ϕ), where ϕ is 90°. ϕ₁ and ϕ₂ shown in FIGS. 1A and 1Brelate to ϕ according to the following equation: 2ϕ=180=ϕ₁−ϕ₂ (orequivalently, 2*Td*ω_(m)/π=1 where Td is the delay of the transmissionlines). As a result of the switching at the switch groups closest tonodes A, the input signal is commutated and two mixing products appearafter the commutation on each transmission line at ω_(in)−ω_(m) andω_(in)+ω_(m). These signals then flow through the top and bottomtransmission lines (which provide −ϕ₁ and −ϕ₂ phase shifts atω_(in)−ω_(m) and ω_(in)+ω_(m), respectively). The mixing tones flowingthrough the top transmission line appear at node B1F with total phaseshifts of −ϕ₁ and −ϕ₂ at ω_(in)−ω_(m) and ω_(in)+ω_(m), respectively.The mixing tones flowing through the bottom line appear at node B2F withtotal phase shifts of −ϕ₁+90° and −ϕ₂−90° at ω_(in)−ω_(m) andω_(in)+ω_(m), respectively. This is shown in graph 102 of FIG. 1B. Thephase shifted signals are then commutated again at ω_(m), by the switchgroups closest to nodes C, but with a phase shift of ϕ. For each of thefour signals in graph 102, two mixing products appear after thecommutation at nodes C (for a total of eight signals). As shown in graph103 of FIG. 1B, the mixing products appear at ω_(in)−2ω_(m), ω_(in), andω_(in)+2ω_(m) with phase shifts as shown in the following table:

Signal in Mixing Resulting Resulting Graph 102 Product Frequency PhaseShift ω_(in) − ω_(m), −ϕ₁ 1 ω_(in) − 2ω_(m) −ϕ − ϕ₁ ω_(in) − ω_(m), −ϕ₁2 ω_(in) ϕ − ϕ₁ ω_(in) + ω_(m), −ϕ₂ 1 ω_(in) −ϕ − ϕ₂ = ϕ − ϕ₁ ω_(in) +ω_(m), −ϕ₂ 2 ω_(in) + 2ω_(m) ϕ − ϕ₂ ω_(in) − ω_(m), −ϕ₁ + 90° 1 ω_(in) −2ω_(m) −ϕ − ϕ₁ + 180° ω_(in) − ω_(m), −ϕ₁ + 90° 2 ω_(in) ϕ − ϕ₁ ω_(in) +ω_(m), −ϕ₂ − 90° 1 ω_(in) −ϕ − ϕ₂ = ϕ − ϕ₁ ω_(in) + ω_(m), −ϕ₂ − 90° 2ω_(in) + 2ω_(m) ϕ − ϕ₂ − 180°

As can be seen, the signals at ω_(in)−2ω_(m) and ω_(in)+2ω_(m) are 180°out of phase and thus cancel out. Also, the signals at ω_(in) all havethe same phase, and thus add up into a single signal with a phase shiftof ϕ−ϕ₁, or 90°−ϕ₁. This is shown in graph 104 of FIG. 1B.

Turning to FIG. 1C, it can be seen that a signal cos(ω_(in)t) can beinjected at nodes C. This is represented in graph 111 of FIG. 1D. Asshown in FIG. 1C, the switch groups are switched by the followingsignals: cos(ω_(m)t); cos(ω_(m)t+ϕ); sin(ω_(m)t); and sin(ω_(m)t+ϕ),where ϕ is 90°. ϕ₁ and ϕ₂ shown in FIGS. 1C and 1D relate to ϕ accordingto the following equation: 2ϕ=180=ϕ₁−ϕ₂ (or equivalently, 2*Td*ω_(m)/π=1where Td is the delay of the transmission lines). As a result of theswitching at the switch groups closest to nodes C, the input signal iscommutated and two mixing products appear after the commutation on eachtransmission line at ω_(in)−ω_(m) (with phase shifts of −ϕ) andω_(in)+ω_(m) (with phase shifts of ϕ). These signals then flow throughthe top and bottom transmission lines (which provide −ϕ₁ and −ϕ₂ phaseshifts at ω_(in)−ω_(m) and ω_(in)+ω_(m), respectively). The mixing tonesflowing through the top transmission line appear at node B1R with totalphase shifts of −ϕ−ϕ₁ and ϕ−ϕ₂ at ω_(in)−ω_(m) and ω_(in)+ω_(m),respectively. The mixing tones flowing through the bottom line appear atnode B2R with total phase shifts of 90°−ϕ−ϕ₁ and −90°+ϕ−ϕ₂ atω_(in)−ω_(m) and ω_(in)+ω_(m), respectively. This is shown in graph 112of FIG. 1D. The phase shifted signals are then commutated again at corn,by the switch groups closest to nodes A. For each of the four signals ingraph 112, two mixing products appear after the commutation at nodes A(for a total of eight signals). As shown in graph 113 of FIG. 1D, themixing products appear at ω_(in)−2ω_(m), ω_(in), and ω_(in)+2ω_(m) withphase shifts as shown in the following table:

Signal in Mixing Resulting Resulting Graph 112 Product Frequency PhaseShift ω_(in) − ω_(m), −ϕ − ϕ₁ 1 ω_(in) − 2ω_(m) −ϕ − ϕ₁ ω_(in) − ω_(m),−ϕ − ϕ₁ 2 ω_(in) −ϕ − ϕ₁ ω_(in) + ω_(m), ϕ − ϕ₂ 1 ω_(in) ϕ − ϕ₂ = −ϕ −ϕ₁ ω_(in) + ω_(m), ϕ − ϕ₂ 2 ω_(in) + 2ω_(m) ϕ − ϕ₂ ω_(in) − ω_(m), 90° −ϕ − ϕ₁ 1 ω_(in) − 2ω_(m) −ϕ − ϕ₁ + 180° ω_(in) − ω_(m), 90° − ϕ − ϕ₁ 2ω_(in) −ϕ − ϕ₁ ω_(in) + ω_(m), ϕ − ϕ₂ − 90° 1 ω_(in) ϕ − ϕ₂ = −ϕ − ϕ₁ω_(in) + ω_(m), ϕ − ϕ₂ − 90° 2 ω_(in) + 2ω_(m) ϕ − ϕ₂ − 180°As can be seen, the signals at ω_(in)−2ω_(m) and ω_(in)+2ω_(m) are 180°out of phase and thus cancel out. Also, the signals at ω_(in) all havethe same phase, and thus add up into a single signal with a phase shiftof −ϕ−ϕ₁, or −90°−ϕ₁. This is shown in graph 114 of FIG. 1D.

As can be seen in FIGS. 1C and 1D, the signals at win incur differentphase shifts in the forward and reverse direction (ϕ−ϕ₁ and −ϕ−ϕ₁,respectively), demonstrating the phase non-reciprocity.

The scattering parameter matrix of the configuration shown in FIG. 1 canbe represented by [S] as follows:

$\lbrack S\rbrack = \begin{bmatrix}0 & e^{j{({{- \varphi} - \varphi_{1}})}} \\e^{j{({\varphi - \varphi_{1}})}} & 0\end{bmatrix}$

where: j is the square root of −1. The −ϕ in the term on the top rightcorner and +ϕ in the term on the bottom left corner show that the phaseis non-reciprocal.

FIGS. 2A, 2B, 2C, and 2D show an example of how non-reciprocal amplitude(an isolator) can be implemented in some embodiments.

Turning to FIG. 2A, it can be seen that a signal cos(ω_(in)t) isinjected at nodes A. This is represented in graph 201 of FIG. 2B. Asshown in FIG. 2A, the switch groups are switched by the followingsignals: cos(ω_(m)t); cos(ω_(m)t+ϕ); sin(ω_(m)t); and sin(ω_(m)t+ϕ),where ϕ is 45°. ϕ₁ and ϕ₂ shown in FIGS. 2A and 2B relate to ϕ accordingto the following equation: 2ϕ=90°=ϕ₁−ϕ₂ (or equivalently, 4*Td*ω_(m)/π=1where T_(d) is the delay of the transmission lines). As a result of theswitching at the switch groups closest to nodes A, the input signal iscommutated and two mixing products appear after the commutation on eachtransmission line at ω_(in)−ω_(m) and ω_(in)+ω_(m). These signals thenflow through the top and bottom transmission lines (which provide −ϕ₁and −ϕ₂ phase shifts at ω_(in)−ω_(m) and ω_(in)+ω_(m), respectively).The mixing tones flowing through the top transmission line appear atnode B1F with total phase shifts of −ϕ₁ and −ϕ₂ at ω_(in)−ω_(m) andω_(in)+ω_(m), respectively. The mixing tones flowing through the bottomline appear at node B2F with total phase shifts of −ϕ₁+90° and −ϕ₂−90°at ω_(in)−ω_(m) and ω_(in)+ω_(m), respectively. This is shown in graph202 of FIG. 2B. The phase shifted signals are then commutated again atω_(m), by the switch groups closest to nodes C, but with a phase shiftof ϕ. For each of the four signals in graph 202, two mixing productsappear after the commutation at nodes C (for a total of eight signals).As shown in graph 203 of FIG. 2B, the mixing products appear atω_(in)−ω_(m), ω_(in), and ω_(in)+2ω_(m) with phase shifts as shown inthe following table:

Signal in Mixing Resulting Resulting Graph 202 Product Frequency PhaseShift ω_(in) − ω_(m), −ϕ₁ 1 ω_(in) − 2ω_(m) −ϕ − ϕ₁ ω_(in) − ω_(m), −ϕ₁2 ω_(in) ϕ − ϕ₁ = 45° − ϕ₁ ω_(in) + ω_(m), −ϕ₂ 1 ω_(in) −ϕ − ϕ₂ = ϕ − ϕ₁= 45° − ϕ₁ ω_(in) + ω_(m), −ϕ₂ 2 ω_(in) + 2ω_(m) ϕ − ϕ₂ ω_(in) − ω_(m),−ϕ₁ + 90° 1 ω_(in) − 2ω_(m) −ϕ − ϕ₁ − 180° ω_(in) − ω_(m), −ϕ₁ + 90° 2ω_(in) ϕ − ϕ₁ = 45° − ϕ₁ ω_(in) + ω_(m), −ϕ₂ − 90° 1 ω_(in) −ϕ − ϕ₂ = ϕ− ϕ₁ = 45° − ϕ₁ ω_(in) + ω_(m), −ϕ₂ − 90° 2 ω_(in) + 2ω_(m) ϕ − ϕ₂ −180°

As can be seen, the signals at ω_(in)−2ω_(m) and ω_(in)−2ω_(m) are 180°out of phase and thus cancel out. Also, the signals at coin all have thesame phase, and thus add up into a single signal with a phase shift ofϕ−ϕ₁, or 45°−ϕ₁. This is shown in graph 204 of FIG. 2B.

Turning to FIG. 2C, it can be seen that a signal cos(ω_(in)t) isinjected at nodes C. This is represented in graph 211 of FIG. 2D. Asshown in FIG. 2C, the switch groups are switched by the followingsignals: cos(ω_(m)t); cos(ω_(in)t+ϕ); sin(ω_(m)t); and sin(ω_(m)t+ϕ),where ϕ is 45°. ϕ₁ and ϕ₂ shown in FIGS. 2C and 2D relate to ϕ accordingto the following equation: 2ϕ=90=ϕ₁−ϕ₂ (or equivalently,4*T_(d)*ω_(m)/π=1 where Td is the delay of the transmission lines). As aresult of the switching at the switch groups closest to nodes C, theinput signal is commutated and two mixing products appear after thecommutation on each transmission line at ω_(in)−ω_(m) (with phase shiftsof −ϕ) and ω_(in)+ω_(m) (with phase shifts of ϕ). These signals thenflow through the top and bottom transmission lines (which provides −ϕ₁and ϕ₂ phase shifts at ω_(in)−ω_(m) and ω_(in)+ω_(m), respectively) Themixing tones flowing through the top transmission line appear at nodeB1R with total phase shifts of −ϕ−ϕ₁ and ϕ−ϕ₂ at ω_(in)−ω_(m) andω_(in)+ω_(m), respectively. On the other hand, the mixing tones flowingthrough the bottom line appear at node B2R with total phase shifts of90°−ϕ−ϕ₁ and −90°+ϕ−ϕ₂ at ω_(in)−ω_(m) and ω_(in)+ω_(m), respectively.This is shown in graph 212 of FIG. 2D. The phase shifted signals arethen commutated again at ω_(m), by the switch groups closest to nodes A.For each of the four signals in graph 212, two mixing products appearafter the commutation at nodes A (for a total of eight signals). Asshown in graph 213 of FIG. 2D, the mixing products appear atω_(in)−2ω_(m), ω_(in), and ω_(in)+2ω_(m) with phase shifts as shown inthe following table:

Signal in Mixing Resulting Resulting Graph 212 Product Frequency PhaseShift ω_(in) − ω_(m), −ϕ − ϕ₁ 1 ω_(in) − 2ω_(m) −ϕ − ϕ₁ ω_(in) − ω_(m),−ϕ − ϕ₁ 2 ω_(in) −ϕ − ϕ₁ ω_(in) + ω_(m), ϕ − ϕ₂ 1 ω_(in) ϕ − ϕ₂ = − ϕ −ϕ₁ ω_(in) + ω_(m), ϕ − ϕ₂ 2 ω_(in) + 2ω_(m) ϕ − ϕ₂ ω_(in) − ω_(m), 90° −ϕ − ϕ₁ 1 ω_(in) − 2ω_(m) −ϕ − ϕ₁ − 180° ω_(in) − ω_(m), 90° − ϕ − ϕ₁ 2ω_(in) −ϕ − ϕ₁ ω_(in) + ω_(m), ϕ − ϕ₂ − 90° 1 ω_(in) ϕ − ϕ₂ = −ϕ − ϕ₁ω_(in) + ω_(m), ϕ − ϕ₂ − 90° 2 ω_(in) + 2ω_(m) ϕ − ϕ₂ − 180°

As can be seen, the signals at ω_(in)−2ω_(m), ω_(in), and ω_(in)+2ω_(m)are 180° out of phase and thus cancel out. This is shown in graph 214 ofFIG. 2D.

As can be seen in FIGS. 2C and 2D, the signal at ω_(in) can only pass inthe forward direction while it is completely attenuated in the reversedirection, showing amplitude non-reciprocity.

FIGS. 2A, 2B, 2C, and 2D describe an isolator configuration, wheresignals can travel in one direction but not the reverse direction. Anisolator is like one arm of a circulator. It is useful because it can beplaced between a power amplifier and its antenna, and it will protectthe power amplifier from back reflections at the antenna.

Another use of the structures of FIGS. 1A, 1B, 2A, and 2B is a 2Dlattice of such structures which can have a programmable signalpropagation based on the phase shifts of the different switches.

Turning to FIG. 3, an example 300 of a circulator architecture inaccordance with some embodiments is shown. As illustrated, circulator300 includes an antenna port 301, a transmitter port 302, a receiverport 304, a non-reciprocal phase component 306, and transmission lines308, 310, and 312. Within non-reciprocal phase component 306, there arepassive mixers 314, 316, 318, and 320, and transmission lines 322 and324.

As shown in FIG. 3, values of signals and components in non-reciprocalphase component 306 may depend on an input frequency (ω_(in)) and amodulation frequency (ω_(m)). Win represents the frequency of operationof the circulator. ω_(m) represents the frequency at which the mixersare modulated. Any suitable frequencies can be used for ω_(in) andω_(m), in some embodiments. For example, in some embodiments,RF/millimeter-wave/Terahertz frequencies can be used. In someembodiments, ω_(in) and ω_(m) may be required to be sized relative toeach other. For example, in some embodiments, the mixing signals atω_(in)+ω_(m) and ω_(in)−ω_(m) should be 180° out of phase orequivalently the following equation may be required to be met: 2ω_(m)T_(d)=180°, where T_(d) is the group delay. More particularly, forexample, in some embodiments, ω_(in) can be 28 GHz and ω_(m) can be 9.33GHz.

Each of the transmission lines in FIG. 3 is illustrated as having a“length” that is based on a given frequency. For example, transmissionlines 308, 310, and 312 are illustrated as having a length equal to λ/4,where λ is the wavelength for a frequency of ω_(in). As another example,transmission lines 322 and 324 are illustrated as providing 180° phasedifference between the signals at ω_(in)+ω_(m) and ω_(in)−ω_(m) orequivalently a group delay of T_(d)=¼(ω_(m)/2π).

Transmission lines 308, 310, 312, 322, and 324 can be implemented in anysuitable manner. For example, in some embodiments, one or more of thetransmission lines can be implemented as C-L-C pi-type lumped sections.In some other embodiments, they may be implemented as truly distributedtransmission lines.

The passive mixers can be driven by signals as shown in FIG. 3, in someembodiments. For example, in some embodiments, mixer 314 can be drivenby a signal cos(ω_(m)t), mixer 316 can be driven by a signalcos(ω_(m)t+ϕ), mixer 318 can be driven by a signal sin(ω_(m)t), andmixer 320 can be driven by a signal sin(ω_(m)t+ϕ), where ϕ is 90° forT_(d)=¼(ω_(m)/2π).

In some embodiments, mixers 314, 316, 318, and 320 shown in FIG. 3 canbe implemented with switch groups 414, 416, 418, and 420, respectively,as illustrated in FIG. 4A. As shown in FIG. 4B, the switch groups inFIG. 4A can each include four switches 402, 404, 406, and 408, in someembodiments.

The switches in the switch groups can be implemented in any suitablemanner. For example, in some embodiments, the switches can beimplemented using NMOS transistors, PMOS transistors, both NMOS and PMOStransistors, or any other suitable transistor or any other switchtechnology.

Switch groups 414, 416, 418, and 420 can be controlled by localoscillator signals LO1, LO2, LO1Q, and LO2Q, respectively, as shown inFIG. 4A, in some embodiments. A timing diagram showing an example ofthese signals with respect to each other is shown in FIG. 4C. In thisdiagram, f_(LO) is equal to ω_(m)/2π. When a local oscillator (e.g.,LO1, LO2, LO1Q, or LO2Q) is HIGH, switches 402 and 408 in thecorresponding switch group are CLOSED and switches 404 and 406 in thecorresponding switch group are OPEN. When a local oscillator (e.g., LO1,LO2, LO1Q, or LO2Q) is LOW, switches 404 and 406 in the correspondingswitch group are OPEN and switches 404 and 406 in the correspondingswitch group are CLOSED.

Turning to FIG. 5, an example of a schematic of a circulator that can beimplemented in accordance with some embodiments is shown. Thiscirculator is generally in the same architecture as shown in FIG. 3,except that transmission line 308 is split in half and part is placeadjacent to the receiver nodes.

Turning to FIG. 6, an example of the architecture of FIG. 3 using1-stage lattice filters instead of transmission lines 322 and 324 (FIG.3) is shown. Any suitable filters can be used. For example, in someembodiments, film bulk acoustic resonator (FBAR) filters, surfaceacoustic wave (SAW) filters, bulk acoustic wave (BAW) filters, and/orany other suitable filters can be used. By implementing large delaysusing SAW or BAW filters, the clock frequency can be even furtherreduced. This can be exploited to design even-higher-linearitycirculators through the use of high-voltage technologies andhigh-linearity switch design techniques.

The circuits described herein can be implemented in any suitabletechnology in some embodiments. For example, in some embodiments, thesecircuits can be implemented in any semiconductor technology such assilicon, Gallium Nitride (GaN), Indium phosphide (InP), Gallium arsenide(GaAs), etc. More particularly, for example, in some embodiments, thecircuits can be implemented in IBM 45 nm SOI CMOS process.

In FIG. 1 the phase shift provided by the non-reciprocal phasecomponent, ϕ−ϕ₁, can be tuned by changing the clock phase, ϕ. Thefrequency at which TX-to-RX isolation is achieved depends on ϕ−ϕ₁, so bytuning ϕ, we can tune the isolation frequency.

Although the disclosed subject matter has been described and illustratedin the foregoing illustrative implementations, it is understood that thepresent disclosure has been made only by way of example, and thatnumerous changes in the details of implementation of the disclosedsubject matter can be made without departing from the spirit and scopeof the disclosed subject matter. Features of the disclosedimplementations can be combined and rearranged in various ways.

What is claimed is:
 1. A circuit, comprising: a first differentialtransmission line having: a first end having a first connection a secondconnection; and a second end having a third connection and a fourthconnection; a first switch having a first side, a second side, and acontrol, wherein the first side of the first switch is connected to thefirst connection; a second switch having a first side, a second side,and a control, wherein the first side of the second switch is connectedto the first connection; a third switch having a first side, a secondside, and a control, wherein the first side of the third switch isconnected to the second connection and the second side of the thirdswitch is connected to the second side of the first switch; a fourthswitch having a first side, a second side, and a control, wherein thefirst side of the fourth switch is connected to the second connectionand the second side of the fourth switch is connected to the second sideof the second switch; a fifth switch having a first side, a second side,and a control, wherein the first side of the fifth switch is connectedto the third connection; a sixth switch having a first side, a secondside, and a control, wherein the first side of the sixth switch isconnected to the third connection; a seventh switch having a first side,a second side, and a control, wherein the first side of the seventhswitch is connected to the fourth connection and the second side of theseventh switch is connected to the second side of the fifth switch; andan eighth switch having a first side, a second side, and a control,wherein the first side of the eighth switch is connected to the fourthconnection and the second side of the eighth switch is connected to thesecond side of the sixth switch.
 2. The circuit of claim 1, furthercomprising: a second differential transmission line having: a first endhaving a fifth connection a sixth connection; and a second end having aseventh connection and an eighth connection; a ninth switch having afirst side, a second side, and a control, wherein the first side of theninth switch is connected to the fifth connection; a tenth switch havinga first side, a second side, and a control, wherein the first side ofthe tenth switch is connected to the fifth connection; an eleventhswitch having a first side, a second side, and a control, wherein thefirst side of the eleventh switch is connected to the sixth connectionand the second side of the eleventh switch is connected to the secondside of the ninth switch; a twelfth switch having a first side, a secondside, and a control, wherein the first side of the twelfth switch isconnected to the sixth connection and the second side of the twelfthswitch is connected to the second side of the tenth switch; a thirteenthswitch having a first side, a second side, and a control, wherein thefirst side of the thirteenth switch is connected to the seventhconnection; a fourteenth switch having a first side, a second side, anda control, wherein the first side of the fourteenth switch is connectedto the seventh connection; a fifteenth switch having a first side, asecond side, and a control, wherein the first side of the fifteenthswitch is connected to the eighth connection and the second side of thefifteenth switch is connected to the second side of the thirteenthswitch; and a sixteenth switch having a first side, a second side, and acontrol, wherein the first side of the sixteenth switch is connected tothe eighth connection and the second side of the sixteenth switch isconnected to the second side of the fourteenth switch, wherein the fifthconnection is connected to the first connection, the sixth connection isconnected to the second connection, the seventh connection is connectedto the third connection, and the eighth connection is connected to thefourth connection.
 3. The circuit of claim 1, further comprising: atleast one differential transmission line having a total delay of threequarters of a period of an operating frequency of the circuit, having afirst side having a ninth connection and a tenth connection, and havinga second side having an eleventh connection and a twelfth connection,wherein the ninth connection is connected to the second side of thefirst switch, the tenth connection is connected to the second side ofthe fourth switch, the eleventh connection is connected to the secondside of the fifth switch, and the twelfth connection is connected to thesecond side of the eighth switch.
 4. The circuit of claim 3, wherein theat least one differential transmission line comprises: a thirddifferential transmission line having a delay of one quarter of theperiod of the operating frequency of the circuit; a fourth differentialtransmission line having a delay of one quarter of the period of theoperating frequency of the circuit; and at least one fifth differentialtransmission line having a total delay of one quarter of the period ofthe operating frequency of the circuit.
 5. The circuit of claim 4,further comprising a transmitter port, an antenna port, and a receiverport, wherein the third differential transmission line is connectedbetween the transmitter port and the antenna port, and the fourthdifferential transmission line is connected between the antenna port andthe receiver port.
 6. The circuit of claim 4, wherein the at least onefifth differential transmission line comprises: a sixth differentialtransmission line having a delay of one eighth of the period of theoperating frequency of the circuit; and a seventh differentialtransmission line having a delay of one eighth of the period of theoperating frequency of the circuit.
 7. The circuit of claim 1, whereinthe control of the first switch and the control of the fourth switch areconnected to a first local oscillator signal, the control of the secondswitch and the control of the third switch are connected to a secondlocal oscillator signal, the control of the fifth switch and the controlof the eighth switch are connected to a third local oscillator signal,and the control of the sixth switch and the control of the seventhswitch are connected to a fourth oscillator signal.
 8. The circuit ofclaim 7, wherein the first oscillator signal and the first oscillatorsignal and the second oscillator signal are 180 degrees out of phase,the third oscillator signal and the fourth oscillator signal are 180degrees out of phase, and the third oscillator signal is delay from thefirst oscillator signal by one quarter of a period of an operatingfrequency of the circuit.
 9. The circuit of claim 8, wherein the firstlocal oscillator, the second local oscillator, the third localoscillator, and the fourth local oscillator each have a 50% duty cycle.10. The circuit of claim 1, wherein the first differential transmissionline has a delay of one quarter of a period of an operating frequency ofthe circuit.
 11. The circuit of claim 1, wherein the first differentialtransmission line is implemented as at least one C-L-C pi-type lumpedsection.